1. Technical Field
The present invention relates to an ultrasonic transducer, an ultrasonic probe, a diagnostic device, and an electronic instrument.
2. Background Technology
An ultrasonic transducer in which a plurality of ultrasonic elements are arranged in a matrix pattern has been known. This ultrasonic transducer includes a substrate that has a plurality of openings, a supporting film that is provided on the substrate so as to cover each of the openings, and a piezoelectric element that is provided on a part of the supporting film corresponding to each of the openings. A diaphragm is constructed by the part of the supporting film corresponding to the opening which is a part coinciding with the opening of the supporting film in a planar view. The ultrasonic element is constructed by the diaphragm and the piezoelectric element provided on the diaphragm.
In this ultrasonic transducer, it has been known that two kinds of ultrasonic elements in which the areas of the diaphragms are different are provided, and are driven at different frequencies (for example, see Patent Document 1). In Patent Document 1, it is considered that the plurality of ultrasonic elements having the larger areas of the diaphragms are electrically connected in parallel with respect to each other. Likewise, it is considered that the plurality of ultrasonic elements having the smaller areas of the diaphragms are electrically connected in parallel with respect to each other.
When the two kinds of ultrasonic elements are compared, since the ultrasonic elements having the larger areas of the diaphragms have low resonance frequency, they are driven at low frequency and generate ultrasonic waves of low frequency. Also, since the ultrasonic elements having the smaller areas of the diaphragms have high resonance frequency, they are driven at high frequency and generate ultrasonic waves of high frequency. In a diagnostic device having an ultrasonic probe that uses this ultrasonic transducer, when a deep part (long distance) of a living body as a test target is diagnosed, ultrasonic waves of low frequency are used for diagnosis because ultrasonic waves of high frequency cannot reach a deep part. On the other hand, when a shallow part (short distance) of a living body is diagnosed, ultrasonic waves of high frequency are used for diagnosis so as to increase the resolution.
However, the sensitivity of an ultrasonic element becomes high as the area of the diaphragm becomes large. Therefore, the well-known ultrasonic transducer has a problem that the sensitivity of the ultrasonic elements having the smaller areas of the diaphragms is lower than that of the ultrasonic elements having the larger areas of the diaphragms. Further, due to the difference in the sensitivity, there is a problem that the magnitude of a signal output from each ultrasonic element is different, and a circuit configuration becomes complicated in order to match the magnitude of the signal.
Japanese Laid-open Patent Publication No. 2006-75425 (Patent Document 1) is an example of the related art.